RD400 and other 2 stroke motorcycles

Mostly vintage two stroke bikes

Sep 26

KH400 Starting problems

Kawasaki’s KH400 sometimes gets hard to start when the engine is warm. KH400’s have CDI (capacitor discharge ignition) systems which are generally great because the timing stays fixed and there are no points to wear out.  However, the electronics, particularly when they are nearly 40 years old, are susceptible to failure.

My KH400 is an interesting example because I bought it in 2012 with only 150 miles on it - 36 years after it was built!  In January 2014 I noticed the electrical system was getting weak.  It didn’t generate enough power to recharge the battery with the headlight on.  I wondered how the coils could break down with so little mileage.  Apparently all it takes is time for the insulating varnish to break down on the copper wires, creating shorts and reducing the charging ability.  I had the stator coils rewired and that problem went away.

Lately the bike was taking lots of kicks to get started, sometimes 10 or more. Jim Hobbs at Lakeland Services sells a replacement parts for Kawasaki triples.  I gave him a call and explained the bike doesn’t have a hard time starting when warm, but it does when the engine is cold.  He said the hard starting problem whether the engine is warm or cold is generally caused by a failing low speed coil.  Okay I want it fixed now so I went and ordered one. Two days later the part arrived in the mail.

Here’s the new coil.  It’s pretty small.

image

And here’s the left side of the KH400 with the stator cover and flywheel removed.  If you need to remove the flywheel, read the KH400 flywheel removal post.  The high speed coil is mounted in front of the low speed coil.  

image

Now we get into the nitty gritty.  First, remove the two long screws that hold the two coils onto the plate.  See the aluminum spacers between the two coils?  Remember to include them when the coils are being reassembled. The low speed coil has epoxy covering the terminals.  The epoxy can be cracked with needle nose pliers and then the wires can gently be removed.  Two white wires attach to the left terminal and a black wire attaches to the right terminal.  Here’s another picture.

image

In the picture above you can see one white wire and one black wire, these are coming off the high speed coil and attaching to the low speed coil.  Another white wire is behind the low speed coil.  If you are like me and not an expert on this stuff, take it one step at a time.

Next, get out the soldering iron and attach the white and black wires to the terminals on the new coil.  The wires might need to be lengthened.  I used some copper strands and ran them through the terminal for the white wires, then soldered the two wires, one to each side of the strands. Insulation - it’s hard to get in there with heat shrink so I used fast drying epoxy to cover the exposed strands and prevent shorts.

Those long screws that hold the coils on are pretty fragile.  Both screws got twisted and damaged when I removed them.  Luckily, City Mill, the local hardware store in Kaimuki, had replacement screws - M4 x 40mm plus a lockwasher for each screw. They were a little longer than the original screws so I cut a few millimeters off each of them with an angle grinder.  

image

Here we are with the high and low speed coils reinstalled.  The other two coils are the stator coils for the charging system.

Next step, install the flywheel and the engine cover.  Oh yeah, and reconnect the battery (I disconnected it at the beginning of the install). Three kicks and the motor was running.  After the bike cooled I tried again and it started with one kick.  The low speed coil replacement fixed the problem!  I’ll be back on the Oahu’s roads tomorrow.


May 23

A sealed battery for the KH400

KH400 battery

kawasaki triple battery

honolulu

It was time for a new battery and sealed batteries are nice because there’s no acid to leak out onto your exhaust pipes, chain, swingarm etc.  The KH400 has an odd sized battery, only 2.5 inches wide.  It’s hard to find a replacement.  Motobatt came to the rescue.  Their MB5.5U fits perfectly and it has these cool universal terminals.  You can attach the battery cables from the side or from the top.  It came in handy on this bike, I attached the ground cable from the front and the positive cable from the top.  Piece of cake, took about 10 minutes and this battery is stronger than a brand new lead-acid battery!

The price was $68 including shipping on e-bay.

Kawasaki’s H2 has the same battery size as the KH400, HOWEVER - H2’s tend to overcharge their batteries and installing a sealed battery with a stock H2 regulator may result in a ruined battery.  So it’s best to stick to a stock unsealed battery for an H2 unless you’ve upgraded to a better regulator.

Here’s where to buy a better H2 voltage regulator: Lakeland Services

And note with this voltage regulator, you don’t even need a battery! However your bike will have no juice until the motor is running.

By the way this same size battery should fit the RZ350 too.  It will also work for the RD400 with some space leftover.  You can keep the battery from moving around in the RD400’s battery box by putting some rubber or foam blocks.  Even folded up cardboard will work.

I’m ready to ride the KH400 around Honolulu again!


Jan 14

KH400 flywheel removal

My 1976 Kawasaki KH400 is lacking in the charging department. I’m planning to send the stator coils to a shop for rewinding, hopefully that will get the battery charging back where it should be.

The stator coils and CDI are behind the flywheel on the left side of the motor.  To get the flywheel off, first remove the small bolt holding it on then use a flywheel puller.  The flywheel puller can be a 16mm x 1.5 bolt or the rear axle off a KH400.

I tried the bolt and the flywheel wouldn’t budge.  Not wanting to remove the exhaust pipes to get the rear axle, I found a KZ1000 front axle with the correct thread size/pitch.  The flywheel still wouldn’t budge.  

Some guys put a small grade 8 bolt in the hole, then put the flywheel puller on.  The small bolt should  push on the crank and pop the flywheel off.  My first try, the bolt bent and got stuck.  I fished it out, went to the hardware store and found a grade 8 then tried again.  Still it wouldn’t come out and I was a little worried about mashing up the threads in the hole.  Then I found the answer!

Pack the hole with grease, then thread the puller on and tighten.  Grease, like brake fluid is not compressible.  Tightening up on the puller, some grease will ooze out through the keyway and around the threads.  Then eventually “pop” the flywheel comes off.  

Note - the crank must be still while you do this, if the motor is in neutral the crank will just turn while you’re trying to tighten.  So put the motor in gear then jam something in between the chain and sprocket.  I used an old washcloth wrapped around a 1 inch pipe.

Make sure not to drop the flywheel on the ground, it’s delicate.

image


Oct 28
Here’s my latest RD400 project.  It’s a 1977 model, bought from an old friend who used to have a collection of RD’s.  He left this one in a cycle shop to have some minor work done by his mechanic friend.  The mechanic got fired and the bike sat for about six years.  Finally, the shop said take the bike or it will be disposed.  
My friend lost the title, which he had never transferred into his name.  I bought the bike for a good price considering no title.  After nearly a year I managed to get it titled.  
There’s one motorcycle project I have ahead of this one (1973 H1 Kawasaki).  So far I’ve picked up a rebuilt crank and Spec2 expansion chambers.  The plan is to repaint the frame, rebuild the motor and fix up everything else that needs fixing up.  The gas tank, top end, seat etc. are sitting around in boxes.
Stay tuned!

Here’s my latest RD400 project.  It’s a 1977 model, bought from an old friend who used to have a collection of RD’s.  He left this one in a cycle shop to have some minor work done by his mechanic friend.  The mechanic got fired and the bike sat for about six years.  Finally, the shop said take the bike or it will be disposed.  

My friend lost the title, which he had never transferred into his name.  I bought the bike for a good price considering no title.  After nearly a year I managed to get it titled.  

There’s one motorcycle project I have ahead of this one (1973 H1 Kawasaki).  So far I’ve picked up a rebuilt crank and Spec2 expansion chambers.  The plan is to repaint the frame, rebuild the motor and fix up everything else that needs fixing up.  The gas tank, top end, seat etc. are sitting around in boxes.

Stay tuned!


Sep 13

Finally an update to the RD400 website

I owned the pictured 1978 RD400E and 1979 RD400F in the early 2000’s and sold them both to the same guy.  The Daytona went first around 2004 and then I sold him the RD400E in 2005.  I had blown both of the bikes’ motors.  After rebuilding the motors and many hours of tinkering, I gave up on having a reliable RD400 for island cruising. 

In 2012 I bought an RZ350 and loved it!  Fast and reliable, making me want to tackle the RD400 motor again.

At present I own several 2-stroke motorcycles, including an RD400 basket case. I’ll try and post regularly to show the progress of the builds.